jquery ajax成功没有显示数据

Question

I have a simple form that passes values to php using serialize. Now what I am trying to do is, when the values are passed to php for processing, display a message to the user based on wether there is any data or if the values are empty. I can get the message to display by not doing the checks and having just echo value say 1 for success. Is there a way to display the echo of the php to the user using my code. Thanks

data: send,
      success: function (data) {
      if (data == ''){
      $('#brtv-result').addClass("result_msg").html(data).show(1000).delay(4000).fadeOut(3000);
      }


if(empty($service) {

echo 'You must select a service level';
}

else
if ($department == "Choose Department"} {

echo 'Please select a department';
}

else
if (empty($authorised)) {

echo 'You must enter an authorised name';
}

else
if ($address == "Choose Address") {

echo 'Please select a retireval address';
}

else
if (empty($boxnumber)) {

echo 'You must enter a box number to retrieve';
}
else
{
echo $boxnumber;
}